I've learned to tolerate the Emulation Station front end for console games. It feels far too flat and dead for an arcade cabinet, but it works on a TV with a controller.
The problem with simply emulating the NES Classic front end on the Pi is that you don't get the multitude of benefits offered by the NES Classic... such as the fast booting, near instant game loading, easily managed save states, power down after inactivity, cut power without the whole thing taking a dump, etc. All of those features are what set it apart from the Pi experience.